var oddEvenList = function(head){
  if(head === null){
    return null;
  }
  if(head.next === null){
    return head;
  }
  let odd = head;
  let even = head.next;
  let evenTemp = head.next;
  while(even.next !== null && even !== null){
    odd.next = even.next;
    odd = odd.next;
    even.next = odd.next;
    even = even.next;
  }
  odd.next = evenTemp;
  return head
}